Method for producing absorbent article

ABSTRACT

[Object] To provide a method for producing an absorbent article comprising a fiber assembly layer of a cellulose acetate fiber, which can sufficiently apply a drug to the cellulose acetate fiber. 
     [Solution] A method for producing an absorbent article, wherein the absorbent article comprises: a fiber assembly layer including a cellulose acetate fiber, and a member including a water absorbent fiber and directly disposed on the fiber assembly layer, and the method comprises: a first step of opening a cellulose acetate tow and collecting a cellulose acetate fiber to form a fiber assembly layer, a second step of spreading a fiber solvent on the fiber assembly layer and drying the fiber assembly layer; a third step of spreading a drug aqueous solution containing an antibacterial agent and/or a deodorizer on the surface where the fiber solvent has been spread of the fiber assembly layer; and a fourth step of mounting the member on the surface where the drug aqueous solution has been spread of the fiber assembly layer.

FIELD OF THE INVENTION

The present invention relates to a method for producing an absorbentarticle comprising a fiber assembly layer of a cellulose acetate fiber.

DESCRIPTION OF THE RELATED ART

An absorbent article such as an incontinence pad, disposable diaper, andsanitary napkin comprises an absorbent body for absorbing and retainingbody fluid excreted from body such as urine and menstrual blood. Theabsorbent body generally includes a water absorbent resin powder, andbody fluid is absorbed and retained in the water absorbent resin powderinside the absorbent body.

As such absorbent article, an absorbent article comprising a celluloseacetate fiber has been proposed. For example, patent literature 1discloses an absorbent article comprising a water absorbent layer and adiffusion layer disposed under the water absorbent layer, wherein awater absorbent resin powder having specific properties is disposed inthe water absorbent layer, and the diffusion layer includes a celluloseacetate fiber (refer to paragraphs 0124 to 0137 of patent literature 1).

In addition, usage of a cellulose acetate fiber as a deodorizer has beenproposed. For example, patent literature 2 discloses a deodorizermaterial comprising a cellulose diacetate fiber and condensed tannin(refer to paragraphs 0023 and 0032 of patent literature 2).

CITATION LIST Patent Literature

-   Patent literature 1: JP 2014-7024 A-   Patent literature 2: JP 2016-187549 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

As described above, conventionally, a deodorizer is applied to a fiberassembly layer of a cellulose acetate fiber. Since the cellulose acetatefiber has low affinity for water, when a drug aqueous solution isdispersed on the fiber assembly layer of the cellulose acetate fiber, acertain time is required for the drug aqueous solution to be taken intothe fiber assembly layer. Therefore, in the production of an absorbentarticle, when a member including a water absorbent fiber is laminated onthe fiber assembly layer of the cellulose acetate fiber on which thedrug aqueous solution has been dispersed, the drug aqueous solutiontends to migrate to the member including the water absorbent fiber. As aresult, there was a problem that the drug cannot be sufficiently appliedto the fiber assembly layer of the cellulose acetate fiber.

The present invention has been made in view of the above circumstances,and an object of the present invention is to provide a method forproducing an absorbent article comprising a fiber assembly layer of acellulose acetate fiber, which can sufficiently apply a drug to thecellulose acetate fiber.

Solution to Solve Problem

The present invention provides a method for producing an absorbentarticle, wherein the absorbent article comprises: a fiber assembly layerincluding a cellulose acetate fiber, and a member including a waterabsorbent fiber and directly disposed on the fiber assembly layer, andthe method comprises: a first step of opening a cellulose acetate towand collecting a cellulose acetate fiber to form a fiber assembly layer;a second step of spreading a fiber solvent on the fiber assembly layerand drying the fiber assembly layer; a third step of spreading a drugaqueous solution containing an antibacterial agent and/or a deodorizeron the surface where the fiber solvent has been spread of the fiberassembly layer; and a fourth step of mounting the member on the surfacewhere the drug aqueous solution has been spread of the fiber assemblylayer.

The fiber solvent is a solvent that can dissolve the cellulose acetatefiber. Such fiber solvent spread on the fiber assembly layer candissolve the surface of the cellulose acetate fiber. Thus, spreading thefiber solvent on the fiber assembly layer and drying the fiber assemblylayer allows the portion where the fibers are in contact with each otherin the layer to be welded. Welding a part of the fiber can suppress thedecrease in the distance between the fibers when spreading the drugaqueous solution, and further speed up the permeation of the drugaqueous solution, Therefore, the spread drug aqueous solutionimmediately disperses in the fiber assembly layer, and even if themember including the water absorbent fiber is mounted directly on thefiber assembly layer, the migration of the drug aqueous solution to themember is suppressed. Thus, the drug can be sufficiently applied to thefiber assembly layer.

Effect of the Invention

According to the present invention, the drug can be sufficiently appliedto the cellulose acetate fiber in the method for producing the absorbentarticle comprising the fiber assembly layer of the cellulose acetatefiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of one example of an absorbent article; and

FIG. 2 is a schematic cross-sectional view along line V-V in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a method for producing an absorbentarticle, wherein the absorbent article comprises: a fiber assembly layerincluding a cellulose acetate fiber, and a member including a waterabsorbent fiber and directly disposed on the fiber assembly layer.

[Absorbent Article]

The absorbent article comprises: a liquid permeable top sheet, a liquidimpermeable back sheet, and an absorbent body disposed between the topsheet and the back sheet and comprising a water absorbent resin powder,wherein the fiber assembly layer is disposed between the back sheet andthe absorbent body. The fiber assembly layer is disposed for the purposeof imparting cushioning property to the absorbent article, and for thepurpose of absorbing and retaining the body fluid reaching the externalsurface of the absorbent body as well.

(Fiber Assembly Layer)

The fiber assembly layer includes the cellulose acetate fiber. Thecellulose acetate fiber is a semisynthetic fiber obtained by esterifyingcellulose with acetate acid. Examples of the cellulose acetate fiberinclude a cellulose diacetate fiber (degree of esterification: 2.22 ormore and less than 2.76) having 74% or more and less than 92% of thehydroxy groups of the cellulose being esterified with acetate acid, anda cellulose triacetate fiber (degree of esterification: 2.76 or more)having 92% or more of the hydroxy groups of the cellulose beingesterified with acetate acid. The cellulose diacetate fiber ispreferable. It is noted that the degree of esterification is an averagenumber of the hydroxy groups substituted by an acetyl group per glucoseunit in the cellulose.

The fineness of the cellulose acetate fiber (monofilament) is preferably0.1 dtex or more, more preferably 0.8 dtex or more, and even morepreferably 1.5 dtex or more, and is preferably 16 dtex or less, morepreferably 12 dtex or less, and even more preferably 8 dtex or less. Ifthe fineness is 0.1 dtex or more, the fiber assembly layer has moreenhanced cushioning property, and if the fineness 16 dtex or less, thefiber assembly layer has better texture.

The cross-sectional shape of the cellulose acetate fiber is notparticularly limited, and may be a circular shape, elliptical shape,triangular shape, L shape, Y shape, X shape, W shape, eight-foil shape,flat shape (such as boomerang shape, wave shape, cocoon shape andcuboidal shape), polygonal shape such as dog bone shape, multifoilshape, hollow shape, or irregular shape. From the standpoint ofenhancing the dryness after absorbing the body fluid, thecross-sectional shape of the cellulose acetate fiber is preferably thecircular shape or elliptical shape.

The fiber assembly layer may further include other fiber than thecellulose acetate fiber. In this case, the amount of the celluloseacetate fiber in the fiber assembly layer is 50 mass % or more,preferably 70 mass % or more, more preferably 90 mass % or more. It isnoted that the fiber assembly layer most preferably consists of thecellulose acetate fiber. Examples of the other fiber include a cellulosefiber, polyester fiber, polyolefin fiber, polyamide fiber, polyvinylalcohol fiber, and acrylic fiber.

The mass per unit area of the fiber assembly layer is preferably 20 g/m²or more, more preferably 30 g/m² or more, and even more preferably 40g/m² or more, and is preferably 150 g/m² or less, more preferably 135g/m² or less, and even more preferably 120 g/m² or less. If the mass perunit area is 20 g/m² or more, the fiber assembly layer has more enhancedcushioning property, and if the mass per unit area is 150 g/m² or less,the fiber assembly layer has better texture.

The thickness of the fiber assembly layer is preferably 1 mm or more,more preferably 1.5 mm or more, and even more preferably 2 mm or more,and is preferably 20 mm or less, more preferably 17.5 mm or less, andeven more preferably 15 mm or less. If the thickness is 1 mm or more,the fiber assembly layer has more enhanced cushioning property, and ifthe thickness is 20 mm or less, the absorbent article is not excessivelybulky, and has better wearing feeling. The thickness of the fiberassembly layer is measured with a thickness gage (SM-130, available fromTECLOCK Co., Ltd.) in a final pressure of 2.2 N or less. An anvil and agauge head used in the measurement have a flat surface which is incontact with the measuring object and has a diameter of 10 mm.

The fiber assembly layer preferably has a low-density region and ahigh-density region having a higher density than the low-density region,in the width direction. It, is preferable that the central region in thewidth direction of the fiber assembly layer is the low-density region,and the regions of the fiber assembly layer on the outer sides in thewidth direction of the low-density region are the high-density regions.Specifically, when one edge of the fiber assembly layer is 0%, anotheredge of the fiber assembly layer is 100%, and the central part in thewidth direction of the fiber assembly layer is 50%, the low-densityregion preferably exists in a range from 25% to 75%, more preferablyexists in a range from 35% to 65%.

When the fiber assembly layer has the low-density region and thehigh-density region, the density ratio of the high-density region to thelow-density region (density of high-density region/density oflow-density region) is preferably 1.2 or more, more preferably 1.3 ormore, and even more preferably 1.4 or more, and is preferably 3 or less,more preferably 2.5 or less, and even more preferably 2 or less. If thedensity ratio is 1.2 or more, fiber amount can be decreased in thecentral part in the width direction of the fiber assembly layer, that isthe urination position, thereby enhancing the permeation of body fluid,and if the density ratio is 3 or less, the edge regions of the fiberassembly layer become less bulky.

The contact points of the constituent fibers in the fiber assembly layerare fixed to each other. If the contact points of the fibers are fixedto each other, the fiber assembly layer has further enhanced cushioningproperty, and has maintained voids between the fibers when the bodyfluid is taken therein, thereby enhancing the body fluid absorbing speed.

The fiber assembly layer preferably has a first region where the fixeddegree of the constituent fibers is low, and a second region where thefixed degree of the constituent fibers is higher than that of the firstregion. It is preferable that the central region in the width directionof the fiber assembly layer is the second region, and the regions on theouter sides in the width direction of the second region of the fiberassembly layer are the first regions. Specifically, when one edge of thefiber assembly layer is 0%, another edge of the fiber assembly layer is100%, and the central part in the width direction of the fiber assemblylayer is 50%, the second region preferably locates in a range from 10%to 90%, The higher fixed degree of the fibers in the central part in thewidth direction can increase the permeation speed of body fluid in thepart corresponding to the urination position of the wearer. The fixeddegree of the constituent fibers can be adjusted by increasing ordecreasing the amount of the fiber solvent which will be describedlater.

It is noted that the second region preferably includes the low-densityregion.

The fiber constituting the fiber assembly layer is provided with eitherof or both of the antibacterial agent and the deodorizer.

The antibacterial agent is not particularly limited, as long as theagent imparts the antibacterial activity to the cellulose acetate fiber,and examples thereof include an organic acid, Examples of the organicacid include butanoic acid, valeric acid, caproic acid, enanthic acid,caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid,palmitic acid, margaric acid, stearic acid, arachidic acid, lactic acid,myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenicacid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipicacid, pimelic acid, suberic acid, azelaic acid, sebacic acid, malicacid, tartaric acid, citric acid, fumaric acid, maleic acid, glutaconicacid, itaconic acid, 2-methylene glutaric acid, aconitic acid, benzoicacid, 2-naphthoic acid, gallic acid, phthalic acid, isophthalic acid,and dehydroacetic acid. Among them, fumaric acid, dehydroacetic acid,and benzoic acid are preferable.

The solubility of the organic acid in water (25° C.) is preferably 0.1g/100 g or more, and is preferably 10 g/100 g or less, more preferably 9g/100 g or less, and even more preferably 8 g/100 g or less. If thesolubility is 10 g/100 g or less, the organic acid adhered to the fiberslowly dissolves in the body fluid or the like, and thus theantibacterial activity thereof can be exerted for a long period of time.

The amount of the organic acid to be add is preferably 0.0001 part bymass or more, more preferably 0.001 part by mass or more, and ispreferably 0.15 part by mass or less, more preferably 0.05 part by massor less, and even more preferably 0.015 part by mass or less, withrespect to 100 parts by mass of the fiber assembly layer. If the amountof the organic acid to be added is 0.0001 part by mass or more, thefiber assembly layer has more enhanced antibacterial effect, and if theamount of the organic acid is 0.15 part by mass or less, adverse effecton skin caused by the excessively high level of the organic acid can besuppressed.

Examples of the deodorizer include a polyphenol compound andcyclodextrin. As the polyphenol compound, an extract obtained fromplants such as pine, hiba, Japanese cypress, cedar, tea, Japanesecamellia, sasanqua, persimmon, bamboo, bamboo grass, sage, thyme,rosemary, eucalyptus, lavender, parsley, apple fruit, grape seed,mushroom and alga can be used. As the plant extract, the extractobtained from plants such as tea, Japanese camellia, sasanqua,persimmon, bamboo, bamboo grass, eucalyptus and grape seed which containa great level of catechins and flavones are preferable, condensed tanninis more preferable.

The amount of the deodorizer to be added is preferably 0.01 part by massor more, more preferably 0.1 part by mass or more, and even morepreferably 1 part by mass or more, and is preferably 50 parts by mass orless, more preferably 30 parts by mass or less, and even more preferably20 parts by mass or less, with respect to 100 parts by mass of the fiberassembly layer. If the amount of the deodorizer to be added is 0.01 partby mass or more, the deodorization effect is further enhanced, and ifthe amount of the deodorizer to be added is 50 parts by mass or less,lowering in the texture of the fiber assembly layer can be suppressed.

The antibacterial agent and the deodorizer can be applied uniformly tothe whole fiber assembly layer, or be applied nonuniformly in differentamounts to the fiber assembly layer. Specifically, the amount of theantibacterial agent and the deodorizer to be applied to the high-densityregion is preferably higher than the amount of the antibacterial agentand the deodorizer to be applied to the low-density region. In addition,the amount of the antibacterial agent and the deodorizer to be appliedto the second region is preferably higher than the amount of theantibacterial agent and the deodorizer to be applied to the firstregion.

(Member Including Water Absorbent Fiber)

The member including the water absorbent fiber is disposed on the fiberassembly layer such that the member is in contact with the fiberassembly layer.

The water absorbent fiber is a more hydrophilic fiber than the celluloseacetate fiber, and specifically is a fiber having a SP (solubilityparameter) value of more than 11.4. Examples of the water absorbentfiber include a cellulose fiber.

Examples of the member including the water absorbent fiber include atissue paper composed of a cellulose fiber, and a water absorbent layerincluding a pulp fiber and a water absorbent resin powder. Examples ofthe combination of the fiber assembly layer and the member include acombination of the fiber assembly layer and the tissue paper wrappingthe fiber assembly layer; a combination of the fiber assembly layer andthe water absorbent layer directly formed on the fiber assembly layer;and a combination of the fiber assembly layer and an absorbent body (aproduct having the water absorbent layer wrapped with the tissue paper)directly disposed on the fiber assembly layer.

(Top Sheet)

The top sheet is disposed on a side of the absorbent article closest tothe wearer to rapidly capture the body fluid from the wearer andtransfer the body fluid toward the absorbent body. As the top sheet, aliquid permeable sheet material, for example, a nonwoven fabric formedof a hydrophilic fiber can be used. The nonwoven fabric used as the topsheet is, for example, a point-bonded nonwoven fabric, air-throughnonwoven fabric, spunlace nonwoven fabric, or spunbond nonwoven fabric.As the hydrophilic fiber for forming these nonwoven fabrics, cellulose,rayon, cotton, and the like are usually used. It is noted that as thetop sheet, a liquid permeable nonwoven fabric formed of a hydrophobicfiber (for example, polypropylene, polyethylene, polyester, andpolyamide) whose surface is hydrophilized with a surfactant may be used.

(Back Sheet)

The back sheet is disposed on an outermost side of the absorbent articleto prevent the body fluid or the like from leaking out. As the liquidimpermeable sheet used as the back sheet, a water-repellent or liquidimpermeable nonwoven fabric (for example, a spunbond nonwoven fabric,meltblown nonwoven fabric, and SMS (spunbond-meltblown-spunbond)nonwoven fabric) formed by a hydrophobic fiber (for example,polypropylene, polyethylene, polyester, polyamide, and nylon), or awater-repellent or liquid impermeable plastic film is used to preventthe body fluid reaching the liquid impermeable sheet from oozing out ofthe absorbent article. When the plastic film is used as the liquidimpermeable sheet, a moisture permeable (air permeable) plastic film ispreferably used from the standpoint of preventing the humid feeling andenhancing the wearer's ccmfortableness.

(Absorbent Body)

The absorbent body can absorb body fluid. The absorbent body includes atleast one water absorbent layer. The water absorbent layer includes thewater absorbent resin powder as the water absorbent material. The waterabsorbent layer may further include the water absorbent, fiber as thewater absorbent material.

As the water absorbent resin powder, a water absorbent resin powder usedin the conventional absorbent article can be used. The water absorbentresin powder is preferably, but not particularly limited to, acrosslinked polymer having acrylic acid as a constituent component andhaving carboxyl groups being at least partially neutralized. The amountof the acrylic acid component constituting the crosslinked polymer ispreferably 50 mass % or more, more preferably 90 mass % or more, andeven more preferably 95 mass % or more, and is preferably 99 mass % orless, more preferably 97 mass % or less. If the amount of the acrylicacid component fails within the above range, the obtained waterabsorbent resin powder easily has the desired absorbent performance.

Examples of the cation for neutralizing at least a part of the carboxylgroups of the crosslinked polymer include, but are not particularlylimited to, an alkali metal ion such as lithium, sodium and potassium;and an alkaline earth metal ion such as magnesium and calcium. Amongthem, at least a part of the carboxyl groups of the crosslinked polymeris preferably neutralized with a sodium ion. It is noted that theneutralization of the carboxyl groups of the crosslinked polymer can beconducted by neutralizing the carboxyl groups of the crosslinked polymerobtained by polymerization, or alternatively be conducted by using amonomer which has been neutralized in advance to form the crosslinkedpolymer.

The neutralization degree f the carboxyl groups of the crosslinkedpolymer is preferably 55 mole % or more, more preferably 60 mole % ormore. If the neutralization degree is excessively low, the obtainedwater absorbent resin powder may have lowered absorbent performance. Inaddition, the upper limit of the neutralization degree is notparticularly limited, and all the carboxylic groups can be neutralized.It is noted that the neutralization degree is calculated according tothe following formula.

Neutralization degree (mole %) 100×[Number of moles of neutralizedcarboxyl groups in crosslinked polymer]/[Total number of moles ofcarboxyl groups in crosslinked polymer (including neutralized andunneutralized carboxyl groups)]

The water absorbent resin powder may further include an additive such asan antiseptic, fungicide, antibacterial agent, antioxidant, ultravioletabsorbent agent, coloring agent, perfuming agent, deodorizer, inorganicpowder, and organic fibrous material. Examples of the water absorbentfiber include a pulp fiber, cellulose fiber, rayon, and acetate fiber.

The water absorbent layer may include a fiber base material in additionto the water absorbent resin powder. Examples of the fiber base materialinclude a thermal bonding fiber. The thermal bonding fiber is used toenhance shape-retention. Specific examples of the thermal bonding fiberinclude a polyolefin fiber such as a polyethylene fiber and apolypropylene fiber, a polyester fiber, and a composite fiber. If thewater absorbent material of the water absorbent layer consists of thewater absorbent resin powder, the water absorbent layer can be madethin. The water absorbent layer including the fiber base material issuperior in dispersibility of body fluid,

(Absorbent Article)

Examples of the embodiment of the absorbent article include anembodiment comprising a liquid permeable top sheet, a liquid impermeableback sheet, and an absorbent body disposed between the top sheet and theback sheet, wherein the fiber assembly layer is disposed between theback sheet and the absorbent body, and the fiber assembly layer iswrapped with a nonwoven fabric composed of a water absorbent fiber; andan embodiment comprising a liquid permeable top sheet, a liquidimpermeable back sheet, and an absorbent body disposed between the topsheet and the back sheet, wherein the fiber assembly layer is disposedbetween the back sheet and the absorbent body, the absorbent bodyincludes a water absorbent layer and a nonwoven fabric wrapping thewater absorbent layer and composed of a water absorbent fiber, and theabsorbent body is disposed directly on the fiber assembly layer.

Next, using an incontinence pad as an example, the absorbent articlewill be specifically described with reference to FIGS. 1 and 2. FIG. 1shows a planar view of an incontinence pad. FIG. 2 shows a V-Vcross-sectional view of the incontinence pad in FIG. 1. It is notedthat, in the figures, the arrow B indicates a width direction, the arrowA indicates a longitudinal direction, and the direction on the planeformed by the arrows A and B is a planar direction.

The incontinence pad absorbent article) 1 shown in FIGS. 1 and 2comprises a liquid permeable top sheet 2, a liquid impermeable backsheet 3, and an absorbent body 5 and a wrapped body 6 disposedtherebetween.

The absorbent body 5 is composed of a first base material 52, a secondbase material 53, and a water absorbent layer 51 disposed therebetween.The water absorbent layer 51 is composed of a pulp fiber and a waterabsorbent resin powder. The absorbent body 5 has an opening 5 a at thecentral part in the width direction. In FIGS. 1 and 2, the example usingthe absorbent body 5 with a gourd shape in a planar view as theabsorbent body is shown, but the embodiment of the absorbent body is notlimited to this. In FIGS. 1 and 2, the absorbent body 5 is composed ofthe first base material 52, the second base material 53, and the waterabsorbent layer 51 disposed therebetween, but the second base material53 may not be disposed so that the top sheet 2 and the water absorbentlayer 51 are in direct contact. In addition, in FIGS. 1 and 2, theabsorbent body 5 has the opening 5 a, but the absorbent body 5 may nothave an opening.

The incontinence pad 1 has the wrapped body 6 on the back sheet side ofthe absorbent body 5. The wrapped body 6 is composed of a fiber assemblylayer 61 of a cellulose acetate fiber and a tissue paper 62 wrapping thefiber assembly layer 61. In addition, the contact points of theconstituent fibers in the fiber assembly layer are fixed to each other.The antibacterial agent and/or deodorizer is supported on the fiberassembly layer of the cellulose acetate fiber.

Side sheets 7 extending along the longitudinal direction A of theincontinence pad 1 are joined to both edges of the top sheet 2 in thewidth direction B. The side sheet 7 is formed of a liquid impermeableplastic film, a water-repellent nonwoven fabric, or the like. A raisingelastic member 8 is provided on the side sheet 7 at an inner edge of theincontinence pad 1 in the width direction. When the incontinence pad 1is used, the inner edges of the side sheet 7 rise toward the skin of thewearer by the contracting force of the raising elastic member 8, bywhich side leakage of the excrement such as urine is prevented.

[Production Method]

The method for producing the absorbent article comprises: a first stepof opening a cellulose acetate tow and collecting a cellulose acetatefiber to form a fiber assembly layer; a second step of spreading a fibersolvent on the fiber assembly layer and drying the fiber assembly layer;a third step of spreading a drug aqueous solution containing anantibacterial agent and/or a deodorizer on the surface where the fibersolvent has been spread of the fiber assembly layer; and a fourth stepof mounting the member on the surface where the drug aqueous solutionhas been spread of the fiber assembly layer.

(First Step)

In the first step, the cellulose acetate tow is opened and the celluloseacetate fiber is collected to form the fiber assembly layer.

The cellulose acetate tow is a fiber bundle of cellulose acetatefilaments. The cellulose acetate tow preferably has 3,000 or morefilaments, more preferably has 5,000 or more filaments, and preferablyhas 1,000,000 or less filaments, more preferably has 900,000 or lessfilaments.

Examples of the method for opening the tow include a method of hangingthe tow on a plurality of opening rolls and increasing the width of thetow with the progress of the tow to open the tow; a method of repeatingtow tension (elongation) and tow relaxation (contraction) to open thetow; and a method of using compressed air to widen and open the tow. Theopening width of the tow is not limited, but it is usually about 100 mmto 300 mm which is the width of the fiber assembly layer. In addition,the mass per unit area of the fiber assembly layer can be adjusted byadjusting the opening degree of the tow.

The fiber assembly layer may be formed directly on the back sheet, or beformed on a sheet material for enhancing shape stability. In addition,the fiber assembly layer is preferably fixed to the back sheet or sheetmaterial with an adhesive.

The fiber assembly layer may be formed to have a uniform or nonuniformdensity along the width direction. For example, the fiber assembly layercan be formed such that the density of the central region in the widthdirection of the fiber assembly layer is lower than the density of theregions of both edges in the width direction of the fiber assemblylayer.

(Second Step)

In the second step, the fiber solvent is spread on the fiber assemblylayer and the fiber assembly layer is dried.

The fiber solvent is a solvent that can dissolve the cellulose acetatefiber. Such fiber solvent spread on the fiber assembly layer candissolve the surface of the cellulose acetate fiber. Thus, spreading thefiber solvent on the fiber assembly layer and drying the fiber assemblylayer allows the portion where the fibers are in contact with each otherin the layer to be welded. Welding a part of the fiber can suppress thedecrease in the distance between the fibers when spreading the drugaqueous solution, and further speed up the permeation of the drugaqueous solution.

Examples of the fiber solvent include triacetin. The spreading amount ofthe fiber solvent is preferably 0.1 g/m² or more, more preferably 0.2g/m² or more, and even more preferably 0.5 g/m² or more, and ispreferably 5 g/m² or less, more preferably 3 g/m² or less, and even morepreferably 1.5 g/m² or less. If the spreading amount is 0.1 g/m² ormore, the fiber solvent can be spread uniformly, and if the spreadingamount is 5 g/m² or less, lowering in the texture of the fiber assemblylayer can be suppressed.

The fiber solvent can be spread uniformly on the whole fiber assemblylayer, or be spread nonuniformly on the fiber assembly layer. The amountper unit area of the fiber solvent spread in the central region in thewidth direction of the fiber assembly layer is preferably higher thanthe amount per unit area of the fiber solvent spread in the regions ofboth edges in the width direction of the fiber assembly layer. Thehigher amount in the central region in the width direction can increasethe fixed degree of the fibers in this region, thereby suppressing thedecrease in the permeation speed of the drug aqueous solution even in acase that the amount of the drug aqueous solution in the central regionin the width direction is increased.

In addition, when the fiber assembly layer has uniform densities, theamount per unit area of the fiber solvent spread in the low-density partof the fiber assembly layer is preferably higher than the amount perunit area of the fiber solvent spread in the high-density part of thefiber assembly layer. Specifically, when the fiber assembly layer isformed in the first step such that the density of the central region inthe width direction of the fiber assembly layer is lower than thedensity of the regions of both edges in the width direction of the fiberassembly layer, the amount per unit area of the fiber solvent spread inthe central region in the width direction is preferably higher than theamount per unit area of the fiber solvent spread in the regions of bothedges in the width direction in the second step.

(Third Step)

In the third step, the drug aqueous solution containing theantibacterial agent and/or the deodorizer is spread on the surface wherethe fiber solvent has been spread of the fiber assembly layer in thesecond step. The drug aqueous solution contains the antibacterial agentand/or the deodorizer.

The amount of the antibacterial agent in the drug aqueous solution ispreferably 0,001 part by mass or more, more preferably 0.01 part by massor more, and even more preferably 0.1 part by mass or more, and ispreferably 50 parts by mass or less, more preferably 5 parts by mass orless, and even more preferably 0.5 part by mass or less, with respect to100 parts by mass of water. If the amount of the antibacterial agent is0.001 part by mass or more, the fiber assembly layer can express theantibacterial effect even if a small amount of the drug aqueous solutionis applied, and if the amount of the antibacterial agent is 50 parts bymass or less, adverse effect on skin caused by the excessive amount ofthe antibacterial agent can be suppressed.

The amount of the deodorizer in the drug aqueous solution is preferably0.01. part by mass or more, more preferably 0.1 part by mass or more,and even more preferably 1 part by mass or more, and is preferably 50parts by mass or less, more preferably 30 parts by mass or less, andeven more preferably 10 parts by mass or less, with respect to 100 partsby mass of water. If the amount of the deodorizer is 0.01 part by massor more, the fiber assembly layer can express the deodorization effecteven if a small amount of the drug aqueous solution is applied, and ifthe amount of the deodorizer is 50 parts by mass or less, the drugaqueous solution has lowered viscosity and thus easily permeates intothe fiber assembly layer.

The drug aqueous solution preferably further contains a surfactant,Inclusion of the surfactant can speed up the permeation of the drugaqueous solution applied to the fiber assembly layer, into the fiberassembly layer. The surfactant is preferably a nonionic surfactant. Whenthe organic acid is used as the antibacterial agent, since the drugaqueous solution becomes acidic, an anionic surfactant will have a lowionization rate and tend to have a lowered interface activity. Inaddition, since the water absorbent resin powder is disposed in theabsorbent article, a cationic surfactant will form an ammonium salt withthe water absorbent resin powder.

Examples of the nonionic surfactant include a polyoxyalkylene type and apolyhydric alcohol type. Examples of the polyoxyalkylene type include apolyoxyalkylene alkyl ether, a polyoxyalkylene fatty acid ester, apolyoxyalkylene polyhydric alcohol fatty acid ester, a polyoxyalkylenealkylphenyl ether, a polyoxyalkylene alkylamino ether, and apolyoxyethylene/propylene block polymer. Examples of the polyhydricalcohol type include a polyhydric alcohol fatty acid ester, a polyhydricalcohol alkyl ester ether, and a fatty acid dialkylol amide. As thenonionic surfactant, the polyoxyalkylene alkyl ether is preferable.

The HLB (Hydrophile Lipophile Balance) value of the nonionic surfactantis preferably 8 or more, more preferably 8.5 or more, and even morepreferably 9 or more, and is preferably 15 or less, more preferably 13or less, and even more preferably 12 or less. If the HLB value is 8 ormore, the nonionic surfactant has better dispersibility in the drugaqueous solution, and if the HLB value is 15 or less, the drug aqueoussolution has an enhanced permeation rate into the fiber assembly layer.In the present invention, the HLB value is calculated according to thefollowing Griffin formula.

HLB value=20×{(molecular weight of hydrophilic moiety)/(total molecular

weight)}

The drug aqueous solution preferably contains the organic acid as theantibacterial agent and contains the nonionic surfactant having the HLBvalue of from 8 to 15 as the surfactant. The organic acid has ahydrophilic group, thus if the HLB value of the surfactant is from 8 to15, the organic acid has further enhanced dispersibility.

The drug aqueous solution preferably contains a polyether-modifiedsilicone, in addition to the antibacterial agent and/or deodorizer, andthe surfactant. Inclusion of the polyether-modified silicone cansuppress the formation of a liquid film between the fibers by the drugaqueous solution applied to the fiber assembly layer. Thus, thepermeation of the drug aqueous solution into the fiber assembly layercan be further speeded up. The polyether-modified silicone is a compoundhaving an alkylene oxide introduced in the backbone and/or side chain ofsilicone.

The HLB value of the polyether-modified silicone is preferably 7 ormore, more preferably 8 or more, and is preferably 12 or less. If theHLB value is from 7 to 12, the polyether-modified silicone has betterdispersibility in the drug aqueous solution and well cracks the liquidfilm between the fibers.

The method for spreading the drug aqueous solution on the fiber assemblylayer is not particularly limited, for example, the drug aqueoussolution can be sprayed on the fiber assembly layer. The amount of thedrug aqueous solution can be suitably adjusted depending on the level ofthe drug, but 1 g to 30 g of the drug aqueous solution is usually usedper 100 g of the fiber assembly layer.

The drug aqueous solution may be spread uniformly on the whole fiberassembly layer, or be spread nonuniformly on the fiber assembly layer.The amount per unit area, of the drug aqueous solution spread in thecentral region in the width direction of the fiber assembly layer ispreferably higher than the amount per unit area of the drug aqueoussolution spread in the regions of both edges in the width direction ofthe fiber assembly layer. The higher spreading amount in the centralregion in the width direction can increase the amount of theantibacterial agent and/or the deodorizer to be added in the urinationposition.

In addition, when the amount per unit area of the drug aqueous solutionspread in the central region in the width direction of the fiberassembly layer is higher than the amount per unit area of the drugaqueous solution spread in the regions of both edges in the widthdirection of the fiber assembly layer, the amount per unit area of thefiber solvent spread in the central region in the width direction of thefiber assembly layer is preferably higher than the amount per unit areaof the fiber solvent spread in the regions of both edges in the widthdirection of the fiber assembly layer in the second step. Specifically,it is preferable that the amount per unit area of the fiber solventspread in the central region in the width direction of the fiberassembly layer is preferably higher than the amount per unit area of thefiber solvent spread in the regions of both edges in the width directionof the fiber assembly layer in the second step, and the amount per unitarea of the drug aqueous solution spread in the central region in thewidth direction of the fiber assembly layer is higher than the amountper unit area of the drug aqueous solution spread in the regions of bothedges in the width direction of the fiber assembly layer in the thirdstep. The higher fixed degree of the fibers in the part where the drugamount is higher can suppress the retainment of the drug aqueoussolution on the surface of the fiber assembly layer even if the amountof the drug aqueous solution is high.

(Fourth Step)

In the fourth step, the member including the water absorbent fiber ismounted on the surface where the drug aqueous solution has been spreadof the fiber assembly layer.

The member includes the water absorbent fiber having higherhydrophilicity than the cellulose acetate fiber. Thus, if the member ismounted on the fiber assembly layer having the drug aqueous solutionremained on the surface, the drug aqueous solution will migrate to themember. However, in the production method according to the presentinvention, the drug aqueous solution contains the surfactant, and thedrug aqueous solution is taken into the fiber assembly layer immediatelyafter the drug aqueous solution is spread on the fiber assembly layer.Thus, even if the member is mounted, migration of the drug aqueoussolution to the member is suppressed.

Examples of the member include a tissue paper and a water absorbentlayer. Thus, specific examples of the third step include a step ofwrapping the fiber assembly layer with the tissue paper; a step offorming the water absorbent layer; and a step of disposing an absorbentbody formed by wrapping the water absorbent layer with the tissue paper,on the fiber assembly layer.

EXAMPLES

Examples of the embodiment of the method for producing the absorbentarticle include the following embodiments 1 to 3.

Embodiment 1

A method for producing an absorbent article, comprising:

a first step of opening a cellulose acetate tow and collecting acellulose acetate fiber to form a fiber assembly layer on a tissuepaper;

a second step of spreading a fiber solvent on the fiber assembly layerand drying the fiber assembly layer;

a third step of spreading a drug aqueous solution containing anantibacterial agent and/or a deodorizer on the surface where the fibersolvent has been spread of the fiber assembly layer;

a fourth step of wrapping the fiber assembly layer with the tissue paperto form a wrapped body;

a fifth step of disposing the wrapped body on a back sheet;

a sixth step of disposing an absorbent body on the wrapped body; and

a seventh step of disposing a top sheet on the absorbent body.

Embodiment 2

A method for producing an absorbent article, comprising:

a first step of opening a cellulose acetate tow and collecting acellulose acetate fiber to form a fiber assembly layer on a back sheet;

a second step of spreading a fiber solvent on the fiber assembly layerand drying the fiber assembly layer;

a third step of spreading a drug aqueous solution containing anantibacterial agent and/or a deodorizer on the surface where the fibersolvent has been spread of the fiber assembly layer;

a fourth step of wrapping a water absorbent layer with a tissue paper toform an absorbent body, and mounting the absorbent body on the surfacewhere the drug aqueous solution has been spread of the fiber assemblylayer; and a fifth step of disposing a top sheet on the absorbent body.

Embodiment 3

A method for producing an absorbent article, comprising:

a first step of opening a cellulose acetate tow and collecting acellulose acetate fiber to form a fiber assembly layer on a back sheet;

a second step of spreading a fiber solvent on the fiber assembly layerand drying the fiber assembly layer;

a third step of spreading a drug aqueous solution containing anantibacterial agent and/or a deodorizer on the surface where the fibersolvent has been spread of the fiber assembly layer;

a fourth step of forming a water absorbent layer comprising a waterabsorbent resin powder and a pulp on the surface where the drug aqueoussolution has been spread of the fiber assembly layer; and a fifth stepof disposing a top sheet on the water absorbent layer.

Reference Signs List

1: absorbent article, 2: top sheet, 3: back sheet, 5: absorbent body,51: water absorbent layer, 52: first base material, 53: second basematerial, 6: wrapped body, 61: fiber assembly layer, 62: tissue paper,7: side sheet, 8: rise elastic member

1. A method for producing an absorbent article, wherein the absorbentarticle comprises: a fiber assembly layer including a cellulose acetatefiber, and a member including a water absorbent fiber and directlydisposed on the fiber assembly layer, the method comprises: a first stepof opening a cellulose acetate tow and collecting a cellulose acetatefiber to form a fiber assembly layer; a second step of spreading a fibersolvent on the fiber assembly layer and drying the fiber assembly layer;a third step of spreading a drug aqueous solution containing anantibacterial agent and/or a deodorizer on the surface where the fibersolvent has been spread of the fiber assembly layer; and a fourth stepof mounting the member on the surface where the drug aqueous solutionhas been spread of the fiber assembly layer.
 2. The method for producingthe absorbent article according to claim 1, wherein an amount per unitarea of the fiber solvent spread in a central region in a widthdirection of the fiber assembly layer is higher than an amount per unitarea of the fiber solvent spread in regions of both edges in the widthdirection of the fiber assembly layer in the second step, and an amountper unit area of the drug aqueous solution spread in the central regionin the width direction of the fiber assembly layer is higher than anamount per unit area of the drug aqueous solution spread in the regionsof both edges in the width direction of the fiber assembly layer in thethird step.
 3. The method for producing the absorbent article accordingto claim 1, wherein the fiber assembly layer is formed such that adensity of a central region in a width direction of the fiber assemblylayer is lower than a density of regions of both edges in the widthdirection of the fiber assembly layer in the first step, and an amountper unit area of the fiber solvent spread in the central region in thewidth direction of the fiber assembly layer is higher than an amount perunit area of the fiber solvent spread in the regions of both edges inthe width direction of the fiber assembly layer in the second step. 4.The method for producing the absorbent article according to claim 1,wherein the antibacterial agent is an organic acid.
 5. The method forproducing the absorbent article according to claim 1, wherein the drugaqueous solution contains a nonionic surfactant having a HLB value offrom 8 to
 15. 6. The method for producing the absorbent articleaccording to claim 1, wherein the drug aqueous solution further containsa polyether-modified silicone.
 7. The method for producing the absorbentarticle according to claim 1, wherein the drug aqueous solution containsthe antibacterial agent in an amount of 0.001 part by mass or more and50 parts by mass or less with respect to 100 parts by mass of water. 8.The method for producing the absorbent article according to claim 1,wherein the drug aqueous solution contains the deodorizer in an amountof 0.01 part by mass or more and 50 parts by mass or less with respectto 100 parts by mass of water.
 9. A method for producing an absorbentarticle, comprising: a first step of opening a cellulose acetate tow andcollecting a cellulose acetate fiber to form a fiber assembly layer on aback sheet; a second step of spreading a fiber solvent on the fiberassembly layer and drying the fiber assembly layer; a third step ofspreading a drug aqueous solution containing an antibacterial agentand/or a deodorizer on the surface where the fiber solvent has beenspread of the fiber assembly layer; a fourth step of wrapping a waterabsorbent layer with a tissue paper to form an absorbent body, andmounting the absorbent body on the surface where the drug aqueoussolution has been spread of the fiber assembly layer; and a fifth stepof disposing a top sheet on the absorbent body.
 10. The method forproducing the absorbent article according to claim 9, wherein an amountper unit area of the fiber solvent spread in a central region in a widthdirection of the fiber assembly layer is higher than an amount per unitarea of the fiber solvent spread in regions of both edges in the widthdirection of the fiber assembly layer in the second step, and an amountper unit area of the drug aqueous solution spread in the central regionin the width direction of the fiber assembly layer is higher than anamount per unit area of the drug aqueous solution spread in the regionsof both edges in the width direction of the fiber assembly layer in thethird step.
 11. The method for producing the absorbent article accordingto claim 9, wherein the fiber assembly layer is formed such that adensity of a central region in a width direction of the fiber assemblylayer is lower than a density of regions of both edges in the widthdirection of the fiber assembly layer in the first step, and an amountper unit area of the fiber solvent spread in the central region in thewidth direction of the fiber assembly layer is higher than an amount perunit area of the fiber solvent spread in the regions of both edges inthe width direction of the fiber assembly layer in the second step. 12.The method for producing the absorbent article according to claim 9,wherein the antibacterial agent is an organic acid.
 13. The method forproducing the absorbent article according to claim 9, wherein the drugaqueous solution contains a nonionic surfactant having a HLB value offrom 8 to
 15. 14. The method for producing the absorbent articleaccording to claim 9, wherein the drug aqueous solution further containsa polyether-modified silicone.
 15. A method for producing an absorbentarticle, comprising: a first step of opening a cellulose acetate tow andcollecting a cellulose acetate fiber to form a fiber assembly layer on aback sheet; a second step of spreading a fiber solvent on the fiberassembly layer and drying the fiber assembly layer; a third step ofspreading a drug aqueous solution containing an antibacterial agentand/or a deodorizer on the surface where the fiber solvent has beenspread of the fiber assembly layer; a fourth step of forming a waterabsorbent layer comprising a water absorbent resin powder and a pulp onthe surface where the drug aqueous solution has been spread of the fiberassembly layer; and a fifth step of disposing a top sheet on the waterabsorbent layer.
 16. The method for producing the absorbent articleaccording to claim 15, wherein an amount per unit area of the fibersolvent spread in a central region in a width direction of the fiberassembly layer is higher than an amount per unit area of the fibersolvent spread in regions of both edges in the width direction of thefiber assembly layer in the second step, and an amount per unit area ofthe drug aqueous solution spread in the central region in the widthdirection of the fiber assembly layer is higher than an amount per unitarea of the drug aqueous solution spread in the regions of both edges inthe width direction of the fiber assembly layer in the third step. 17.The method for producing the absorbent article according to claim 15,wherein the fiber assembly layer is formed such that a density of acentral region in a width direction of the fiber assembly layer is lowerthan a density of regions of both edges in the width direction of thefiber assembly layer in the first step, and an amount per unit area ofthe fiber solvent spread in the central region in the width direction ofthe fiber assembly layer is higher than an amount per unit area of thefiber solvent spread in the regions of both edges in the width directionof the fiber assembly layer in the second step.
 18. The method forproducing the absorbent article according to claim 15, wherein theantibacterial agent is an organic acid.
 19. The method for producing theabsorbent article according to claim 15, wherein the drug aqueoussolution contains a nonionic surfactant having a HLB value of from 8 to15.
 20. The method for producing the absorbent article according toclaim 15, wherein the drug aqueous solution further contains apolyether-modified silicone.